Research Of Cooperative Relay Selection And Power Allocation Optimization Scheme

With the rapid development of the internet and multimedia technology, the new generation of wireless communication system is hoped to offer higher data transmission speed and more reliable quality of service. The multi-antenna technology can significantly enhances the system transmission performance and spectral efficiency, and it has been aroused wide attention presently. As an extension of multi-antenna technology, cooperative diversity technology has become a hotspot in the field of communication in recent years, which is also considered as one of the key technologies of the new generation wireless communication system. In a multi-user environment of cooperative diversity technology, each antenna user not only transmits its own information, but also sends information of its partners. A virtual multi-antenna matrix is constituted by the cooperation between nodes, which can obtain a larger diversity gain for mobile users and reduce the fading of wireless channels. However, in many relay coordination scenarios, the optimal collaboration and forwarding relay node must be selected in order to make the system resources more effective. According to the above analysis and the shortcomings of traditional relay node selection algorithm and the power allocation algorithm, this paper proposes a nearest-relay selection algorithm and the power allocation algorithm based on the energy efficiency maximization. The main work of this paper is as follows:Firstly, this paper analyzes the interrupt probability and the diversity gain of different cooperative relay protocol according to the basic performance indicators of cooperative diversity technology, and then analyzes the relay optimal power allocation, including amplify-and-forward and decode-and-forward. The simulation results show that the adaptive relay technology has better performance than the fixed relay technology, and incremental amplify-and-forward protocol has the best performance when comparing with the commonly used relay selection protocol.Secondly, by analyzing the advantages and disadvantages of the traditional relay selection protocol and researching the randomness of the large scale path loss of the correlated channel and the spatial random distribution of user node in network, this paper proposes a nearest-relay selection algorithm based on incremental selection amplify-and-forward protocol. The main idea of this algorithm is that a node broadcasts a paging signal to its neighbor nodes, and then chooses the maximum receiving SNR node as its optimal relay. The results of the simulation of this algorithm are closer to theoretical limitation of the Genie-aided algorithm, and it has a significant performance gains compared to the direct transmission and distributed cooperative transmission respectively. Additionally, the results show that the proposed algorithm can significantly extend the signal coverage and improve the system performance.Finally, a power allocation algorithm based on maximizing efficiency is proposed for considering the overhead of collaboration. This algorithm can works in both single-relay scenario and multi-relay scenario. It chooses the maximize energy efficiency as an indicator to select the optimal data transmission mode and then allocates power for the cooperative nodes combined reasonably. Simulation results show that the collaboration overhead of this algorithm is greater than the collaboration gain when the distance between the source and the end is close, while that of the direct transmission is more effective. However, when the distance increases, the sending power consumption accounts for the most proportion of the total power consumption. In this situation, and the optimal power allocation can minimize the total power consumption in the cooperative system. The simulation results can also help select the optimal relay number for the specific communication system, but increasing the number of the relay is not always good.